Sex determination of Microtus mandarinus mandarinus is independent of Sry gene.

PCR was performed with primers corresponding to the Sry HMG-box of the mouse and eight Microtus species. Primers for the SALL4 gene and the ZFY/ZFX gene were used as positive controls. None of these sets of primers can amplify any homologous segment of the Sry gene in the genomic DNA of Microtus mandarinus mandarinus, but both can amplify the Sry HMG-box in the male mouse, SALL4 bands, and ZFY/ZFX bands in both male and female M. m. mandarinus and mouse. Southern blotting was also used. We used primers for the mouse Sry HMG-box to amplify the Sry HMG-box of the mouse, Microtus arvalis (Microtus), and Pitymys duodecimcostatus (Microtus). The probes were labeled with digoxigenin using PCR after being sequenced. Southern blots were used to detect the genomic DNA of M. m. mandarinus using alkaline phosphatase detection. The results showed that there was a 3.95-kb-blotting band in positive controls: mouse, Microtus arvalis, and Pitymys duodecimcostatus. However, no homologous sequence of the Sry HMG-box was detected in the genomic DNA of M. m. mandarinus. Therefore, we speculate that the Sry HMG-box of M. m. mandarinus is absent or had a big change; sex determination of M. m. mandarinus is independent of Sry. The sex determination mechanism without Sry of M. m. mandarinus is also discussed.